Introduction

For over 50 years, members of our staff
have performed scientific research on the effects of air pollutants
on the environment. There are hundreds of pages on this web site
that focus on the various aspects associated with air pollution
research. In order to assist you in identifying which pages might
be of interest to you, this introduction provides insight into
some of the more important scientific issues. At anytime, please
feel free to visit our Table of Contents.

From our years of experience, we have learned
that it is what we know about pollutant exposure and its effects
on humans and the ecosystem that are the most important aspects
of selecting appropriate standards to protect the public. Using
the most current research information, we continuously assess
the scientific rationale for air pollution standards promulgated
nationally and internationally. Our research sponsors are government,
industry, and environmental groups. Both national and international
institutions support our research efforts. Thousands of individuals
from around the world visit our web pages weekly. Some of the
most popular web pages visited are those associated with (1) natural background of surface
ozone, (2) the biological importance of the higher hourly average
air pollution concentrations more than the mid- and lower-level
values, (3) our exposure- and dose-response research on vegetation
and human health, (4) the "piston effect" and how it
affects the reduction of hourly average surface ozone concentrations
as air pollutant emissions are reduced, (5) our global sulfur
emissions database from 1850-1990, (6) spatial interpolation
of surface ozone (i.e., kriging), (7) concerns about assumptions
associated with epidemiological modeling, (8) our peer-review
publications list, and (9) our Albert Einstein quotations with
references.

For ozone, an important phenomenon is the
"piston effect".
The EPA has confirmed the existence of the effect that was first
described by A.S.L. & Associates in November 1996
and published in the peer-review literature in 1997 and 1998.
The Agency, after reviewing 25 years of air quality data, reported
that there were larger reductions in the higher ozone concentrations
than the middle values. To attain the 8-hour ozone standard of
0.075 ppm or the new 0.070 ppm standard, the high to upper middle
concentration values must be reduced. The "piston effect"
defines whether the 8-hour ozone standard is achievable or just
a bureaucratic goal. Most recent emission reduction modeling
by the EPA and research groups is illustrating the importance
of the "piston effect" in attaining the 8-hour standard.
Based on scientific evidence that has been published in the peer-review
literature, there is concern among some scientists and engineers
that the 8-hour ozone standard may become an elusive goal that
will continue to be violated in many locations in the United
States long after control strategies are implemented. In the
EPA's published trends report for ozone (http://www.epa.gov/airtrends/ozone.html),
the Agency indicated that
O3 levels are still decreasing nationwide, but the rate of decrease
for both the 1-hour and 8-hour levels slowed during the 1990s.
The findings show that the "piston
effect" may be affecting the ability of the Nation to attain
the 8-hour ozone standard everywhere. If the limitations associated
with the"piston effect" are ignored, the EPA and others
will continue to push for greater emission reductions that will
not necessarily result in improvement to surface ozone levels.
For more information on this important subject, please click
here.

At a meeting that took place on August
24-25, 2006 in Durham,
NC, the EPA's Clean Air Scientific Advisory Committee (CASAC)
recommended a more stringent standard than the 8-hour 0.08 ppm
ozone standard. The majority of CASAC's members recommended an
8-hour ozone standard of 0.070 ppm. The selection of 0.070 ppm
implies that a design value of 0.071 ppm would violate a 0.070
ppm standard. There is considerable uncertainty associated with
the (1) epidemiological evidence and (2) data points at the 0.04
and 0.06 ppm levels in the EPA's dose-response function derived
from the controlled human exposure experiments. For the secondary
ozone standard, CASAC recommended the W126 cumulative exposure index integrated over a 3-month growing
season period measured daily from 0800 to 1959 hr. In June 2007,
the EPA Administrator proposed the W126 index as the secondary
ozone standard. Such a secondary ozone standard, in its current
form, would overestimate vegetation effects. Both the primary
and secondary standard recommendations by CASAC were reflected
in the final version of the EPA Ozone Staff Paper. On March 12,
2008, the EPA Administrator made the final decision on the human
health and vegetation ozone standards. EPA revised the 8-hour
"primary" ozone standard, designed to protect public
health, to a level of 0.075 parts per million (ppm). EPA decided
not to adopt the W126 exposure index. Although the EPA
Administrator recommended the W126 as the secondary ozone standard,
based on advice from the White
House (Washington
Post, April 8, 2008; Page D02), the EPA Administrator made the
secondary ozone standard the same as the primary 8-hour average
standard (0.075 ppm). In May 27, 2008, health and environmental
organizations filed a lawsuit arguing that the EPA failed to
protect public health and the environment when it issued in March
2008 new ozone standards. On March 10, 2009, the US EPA requested
that the Court vacate the existing briefing schedule and hold
the consolidated cases in abeyance. EPA requested the extension
to allow time for appropriate EPA officials that were appointed
by the new Administration to review the Ozone NAAQS Rule to determine
whether the standards established in the Ozone NAAQS Rule should
be maintained, modified, or otherwise reconsidered. EPA further
requested that it be directed to notify the Court and the Parties
within 180 days of the Court's order vacating the briefing schedule
of the actions the Agency has taken or intends to take, if any,
with regard to the Ozone NAAQS Rule, and the anticipated time
frame for any such actions.

On September 16, 2009,
the EPA announced it would reconsider the 2008 national ambient
air quality standards (NAAQS) for ground-level ozone for both
human health and environmental effects. The Agency planned to
propose any needed revisions to the ozone standards by December
2009 and issue a final decision by August 2010. On January 7,
2010, the EPA announced on its web site its proposal to strengthen
the national ambient air quality standards for ground-level ozone.
The EPA's proposal decreased the 8-hour primary ozone
standard level, designed to protect public health, to a level
within the range of 0.060-0.070 parts per million (ppm). EPA
also proposed to establish a distinct cumulative, seasonal secondary
standard, referred to as the W126 index, which was designed to protect
sensitive vegetation and ecosystems, including forests, parks,
wildlife refuges, and wilderness areas. EPA proposed to set the
level of the W126 secondary standard within the range
of 7-15 ppm-hours. The proposed revisions resulted from a reconsideration
of the identical primary and secondary ozone standards set at
0.075 ppm in March 2008. On August 20, the Agency announced that
it would delay its final announcement to on or around the end
of October. In early November, the EPA announced that it would
reach a final decision on the ozone standards by December 31,
2010. On December 8, the EPA announced that it would delay its
final decision on the ozone standards until July 2011. EPA announced
on July 26 that it would not make a decision on the ozone standards
by its previously announced deadline of July 29. On September
2, 2011, President Obama requested that the EPA withdraw its
proposal to revise the ozone standards.

On
November 26, 2014, the EPA Administrator announced that she was
proposing an ozone human health (primary) standard in the range
of 65 to 70 ppb and would take comment on a standard as low as
60 ppb. For the welfare (secondary) ozone standard, she proposed
that the standard be the same as the health standard IF the final
health standard were set in the range of 65 to 70 ppb. The rationale
for the EPA proposal can be found at the EPA website. The Administrator believed that a health
standard in this range would protect vegetation from ozone exposures
of W126 values within the range of 13-17 ppm-h. She also took
comment on setting a W126 value in the range of 7-13 ppm-h, which
implied that she was still considering establishing a secondary
standard separate in form from the human health 8-h standard.
In August 2014, the EPA Staff recommended to the Administrator
that she select the ozone primary standard at a specific level
between 60-to-70-parts-per-billion. For the secondary standard,
the EPA Staff recommended that the Administrator establish a
3-month, 12-h W126 secondary standard, which
would have a specific value within the range of 7 to 17 ppm-h.
On October 1, 2015, the EPA Administrator announced that both
the human health and vegetation ozone standards were to be 70
ppb.The
Administrator concluded that protection of vegetation from adverse
effects could be provided by an 8-h ozone standard of 70 ppb
that limits cumulative 3-month seasonal W126 exposures to 17
ppm-hrs or lower. The 70 ppb 8-h ozone standard as per the US
EPA's 2015 decision currently serves as a surrogate to achieve
ozone levels at or below a W126 value of 17 ppm-hrs.

There are still many uncertainties associated
with the science that was used to support the development of
the 8-hour ozone standard. For over 35 years, environmental groups,
industry, and government officials have worked with A.S.L. &
Associates to provide them with the latest scientific information
on ozone and particulate matter. We have carefully noted the
limitations of the science involved in the decision-making process. The June 1997Feature Article in Environmental
Science & Technology, the September 1997 New Directions
Column in Atmospheric Environment, the June 1998 Policy
Analysis article in Environmental Science & Technology,
the May 2001 peer-reviewed paper in the Journal of Geophysical
Research discusses several of the important issues described
on the various web pages associated with this site and the uncertainties
associated with the underlying science. Four important issues
that we address in these web pages are

Based on a review of actual ozone concentration
information and our own research results, actual background ozone
levels are more of a problem than researchers and policymakers
believe. Background ozone plays a very
important role in attaining the 8-h ozone standard across the
U.S.

Is there a way to get around the "piston
effect"? Probably not. The "piston
effect" apparently controls the ability of a specific
violating area reaching attainment in a reasonable time frame.
The result of this effect is that the 8-hour ozone standard of
0.070 ppm may actually be a "target" at some sites
that may never be achieved in the United States. The June 1998
policy analysis article in the peer-reviewed journal, Environmental
Science & Technology, discusses this effect in detail.
Additional articles dealing with the difficulty in achieving
the new standard have been published in peer-reviewed journals.
For a review of some of these articles, please visit our publications page. The "piston effect"
will limit our ability at some sites to consistently attain the
8-hour ozone standard of 0.070 ppm. What causes the "piston
effect"? Our most current research results are providing
the answers to what causes the effect.

What is the result of EPA using chemistry
transport models to generate highly uncertain estimates for background?
Actual levels of background ozone are higher than the models
suggest and therefore, inadequate estimates of background ozone
concentrations will result in an overestimate
by the EPA of the human health risks associated with 8-hour ozone
levels, as well as the ability to attain lower proposed standard
levels. We have combined modeling results with estimates of the
importance of the contributions from the natural sources such
as stratospheric ozone. These results can be found in our publications
listed in our publications page.

The EPA has indicated a pattern
of inconsistent results in epidemiological time-series studies
that is troubling. The epidemiological evidence has played a
disproportionately large role in the policy making process. Time-series
findings indicate associations of mortality with not only PM
and ozone, but with all of the criteria pollutants. Because results
of time-series studies implicate all of the criteria pollutants,
findings of mortality time-series studies do not seem to allow
us to confidently attribute observed effects specifically to
individual pollutants. This raises concern about the utility
of these types of studies in the current NAAQS-setting process.
The EPA Administrator in October 2015 agreed that the epidemiological
risk results did not provide strong evidence for reducing the
current level of the ozone standard. We have commented on the
limitations associated with the use of epidemiological results in the current NAAQS-setting process.

Scientists, engineers, and policy makers
are focusing their attention on assessing how attainable a 0.070
ppm 8-hour ozone standard is without agency exemptions for naturally
occurring violations. A.S.L. & Associateshopes you will take the time
to carefully read the scientific material provided here and learn
more about the science that will affect our ability to meet the
0.070 ppm 8-hour ozone standard. Much of our attention in the
last few years has been focused on background, the frequency
distribution (i.e., rollback) scenarios that result from emission
reductions in NOx and VOCs, human health and vegetation dose-response
modeling, and the shortcomings associated with epidemiological
modeling. We appreciate having the opportunity to provide you
with our research information. If you desire further information,
please contact A.S.L. & Associates.

By introducing the 8-hour ozone standard
in 1997, the U.S. EPA began an unintentional experiment to quantify
how important anthropogenic emissions are in comparison with
natural emissions and processes. In June 2000, Canada joined
the experiment by passing an 8-hour ozone standard of 0.065 ppm.
California has passed an 8-hour, 0.070 ppm ozone standard. The
"piston effect", a natural controller of ozone concentrations,
will probably dominate the ability of states to attain the 8-hour
ozone standard. We continue to perform our research and report,
both in the peer-review literature and on this web page, our
results. If you are interested in becoming a sponsor of our
on-going research, we welcome the opportunity to work with you.
We hope you will return to our web page again and again to
continue to learn more about this most fascinating topic.

Besides our focus on surface ozone on our
web page, we also perform research on particulate matter, epidemiological
methodologies, risk assessment, and other important scientific
topics. Our most current research on the epidemiological methodologies
is showing serious concerns
about the statistical approaches used in assessing the effects
of both particulate matter and ozone on human health. We have
provided a Multimedia Center web
page that provides material that will help you understand the
important scientific issues that we have been addressing over
the past several years. Thank you for taking the time to visit
our web page and we hope that the material provided on these
pages is helpful to you.

Science is both interesting and fun. It
is when policy makers attempt to work with the current state
of science that things really get exciting. Science is the search
for truth. Sometimes we have answers and sometimes we do not.
However, scientists have an obligation to provide guidance to
policy makers whether requested or not to assure that scientific
facts are presented in such a manner that they are accurate and
not obfuscated for political purposes. The purpose of this web
page is provide the general public, scientists, policy makers,
and decision makers the opportunity to review the science that
helps make the decisions that influence the direction in which
our environmental policies are directed. As indicated above,
every week thousands of visitors from around the world read the
materials contained within our web pages. To start your visit
on our web pages, please visit our Table
of Contents or News sections. Welcome
aboard!